1. Field of the Invention
The present invention relates to a backlight apparatus, a control method for controlling the same, and an image display apparatus.
2. Description of the Related Art
An image display apparatus is generally constructed such that a backlight apparatus, which emits or radiates the white light, is combined on a back surface of a color liquid crystal panel which has a color filter. As for the light source of the backlight apparatus, a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or the like has been in the mainstream. In recent years, an LED backlight apparatus, which uses, as a light source, a light emitting diode (LED) that is superior in view of the electric power consumption, the service life, the color reproducibility, and the environmental load, is also progressively used.
Japanese Patent Application Laid-open No. 2001-142409 describes an image display apparatus wherein an area of an LED backlight apparatus, which corresponds to a display area of a liquid crystal panel, is divided into a plurality of blocks (hereinafter referred to as “LED blocks”), LED is provided for each of the LED blocks, and the luminance of LED of each of the LED blocks can be controlled independently. The luminance is lowered for the LED block for radiating the light onto the area which displays a dark screen image and which is included in the display area of the color liquid crystal panel. Thus, the electric power consumption is reduced, and the contrast of a displayed image is improved. The luminance control for LED, which is performed for each of the LED blocks corresponding to the content (brightness) of the displayed image as described above, is referred to as “local dimming control”.
Japanese Patent Application Laid-open No. 2008-159550 relates to a direct type backlight apparatus having LED's arranged for a plurality of partitioned LED blocks respectively, which discloses a method for measuring the luminance of each of the LED blocks by guiding the light of LED of each of the LED blocks to an external measuring apparatus by means of, for example, an optical fiber to perform the measurement.